1. Field of the Invention
The present invention relates to a calibration apparatus and method for calibration of a network analyzer used for measuring a device under test (DUT).
2. Discussion of Related Art
A signal input to or output from a device under test (DUT) is measured to test the DUT. For example, to test a radio frequency (RF) electronic circuit corresponding to a DUT, it is necessary to measure a reflected and transmitted RF signals through the DUT. To measure such RF signal, a network analyzer is generally used.
However, since an error occurs in the network analyzer depending on time and environment, it is necessary to calibrate the error of the network analyzer before testing the DUT. The error of the network analyzer may be modeled into several items and the modeled error items are calculated using measured data to calibrate the error of the network analyzer, which is called calibration.
A calibration method generally used is calibrating errors of a network analyzer by measuring known impedances instead of the DUT. Here, the known impedances are referred to as a standard impedance. Calibration is performed by applying several error items and at least one standard impedance is necessary for this. Also, a detailed calibration method may vary according to the standard impedance that is used. As standards generally used now, there are Short, Open, Load, Through (SOLT) standards, Through, Reflection, Line (TRL) standards, or Line1, Reflection, Line2 (LRL) standards that are another form of TRL standards. For example, when SOLT standards are used, an operation of connecting to ports of the network analyzer with each of a short impedance, an open impedance, a load impedance, and a thru impedance is needed. That is, a time for connecting standard impedances occupies a considerable part of the entire time of performing calibration.
The invention of collecting standard impedances in one main body to reduce the time of performing calibration may refer to FIG. 1 of Korean Utility Model Registration No. 20-0458604. However, in this case, to perform calibration, it is necessary to manually connect ports of a network analyzer with several standard impedances. The connection between the ports with the standard impedances one by one is a complicated and time consuming works.
To solve this, electrically controlled calibration kits for network analyzers have been developed by network analyzer manufacturers. It may be know through FIG. 1 that the electrically controlled calibration kits each generally include RF ports, a circuit portion including standard impedances, and a communication terminal.
FIG. 1 is a reference view illustrating a conventional calibration kit. Referring to FIG. 1, each of the calibration kits includes a communication terminal 50 for communication with each network analyzer and RF ports 52 for being connected with the RF ports of the network analyzer. All the electrically controlled calibration kits of FIG. 1 have no compatibility with products of other companies than a manufacturer of the network analyzer. This is because an existing subject of performing calibration is the network analyzer and a controller of the network analyzer is in charge of all operation and control functions. Thus, it is a very large weakness that a calibration kit of the same manufacturer as that of the network analyzer should only be used.
Also, since the RF ports of the electrically controlled calibration kit should be the same connector type connectable with RF ports of a DUT to precisely measure the DUT after calibration, it is necessary to use various electrically controlled calibration kits. Accordingly, since a large number of electrically controlled calibration kits having various types of RF ports are necessary, a financial cost occurs.